JPS6342012A - Thin film magnetic head - Google Patents

Abstract

PURPOSE:To maximize the output per unit inductance and obtain a head superior in C/W (carrier to noise ratio) by specifying the magnetic path length of a magnetic circuit formed with upper and lower magnetic cores. CONSTITUTION:A magnetic film 2 formed on a nonmagnetic substrate 1 consisting of glass ceramics or the like is used as the lower magnetic core, and a magnetic film 3 formed on the magnetic film 2 with gap materials 4, a signal coil 6, and an insulating material 5 between them is used as the upper magnetic core, and magnetic films 2 and 3 form the magnetic circuit. A magnetic path length lm(mm) of the magnetic circuit formed with upper and lower magnetic cores 3 and 2 is set to the range from 0.3 to 0.5. Thus, the coil resistance is increased to increase the head impedance, and C/N is maximized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic head, and particularly to a thin film magnetic head suitable for VTRs and the like.

[Conventional technology]

An example of a thin film magnetic head for recording and reproducing video signals and the like is a thin film magnetic head described in Japanese Patent Laid-Open No. 55-84019. In this magnetic head, the width of the yoke structure is gradually increased behind the magnetic pole tip region, and the thickness of the magnetic layer is increased by about 60%. This counters saturation of the yoke structure and increases efficiency.

However, - lastly, no consideration is given to the output per unit inductance in consideration of magnetic velocity leakage, and this point is not taken into consideration in the invention described in the above-mentioned publication.

Furthermore, conventionally, the width of the magnetic layer forming the yoke structure has not been considered.As the width of the magnetic layer increases, the efficiency of the magnetic head increases, but at the same time, leakage between the upper and lower magnetic layers also increases. The performance of a normal magnetic head requires reproduction output at a certain inductance, so if the width of the magnetic layer is made larger than necessary, the inductance becomes too large, and as a result, the inductance increases. In order to achieve the specified value, it is necessary to reduce the number of turns of the signal coil, and as a result, no improvement in output per unit inductance can be expected.

Conventionally, there has been no mention of the inclination angle of the slope section from the front working gap forming section (to the upper part of the ε coil) and the interval between the upper and lower air layers.

Magnetic leakage changes greatly depending on the inclination angle and spacing, and unless the shape is optimized, the inductance will increase and the output will decrease due to glue cage (leakage) in that part, and no improvement in performance can be expected.

Furthermore, by reducing the magnetic path length, magnetic flux leakage is reduced and efficiency is increased, but the width of the signal coil between the front actuation gap and the upper and lower magnetic core connections is reduced, which increases coil resistance. However, no consideration was given to the increase in head impedance noise.

[Problem that the invention seeks to solve]

In the above conventional technology, no consideration is given to the width of the magnetic layer forming the yoke structure, and although the efficiency of the magnetic head increases as the width of the magnetic layer increases, at the same time leakage between the upper and lower magnetic layers also increases. Normally, the performance of a magnetic head requires reproduction output at a certain inductance, so if the width of the magnetic layer is made larger than necessary, the inductance becomes too large, and as a result, the inductance becomes too large. In order to achieve this value, it was necessary to reduce the number of turns of the signal coil, and as a result, there was a problem in that performance per unit inductance could not be improved.

In addition, no consideration was given to the inclination angle of the slope section from the front actuation gap forming part to the top of the signal coil, and the spacing between the upper and lower air layers. Magnetic leakage changes greatly depending on the inclination angle and the spacing, and the optimum There was a problem in that performance could not be improved unless the shape was changed.

Furthermore, the magnetic path length, which is the length of the streamline of the magnetic flux, changes depending on the distance between the front operating gap and the upper and lower magnetic core connection parts, and the magnetic path length is reduced! nThe magnetic resistance decreases and the output increases0, but the signal coil width decreases, which increases the coil resistance and increases the impedance noise.If the magnetic path length is not optimized, the C/N There was a problem in that it was not possible to improve the overall performance (output-to-noise ratio).

The present invention maximizes the output per unit inductance and reduces C/N (Carrier to No.
The purpose of the present invention is to provide a thin film magnetic head with an excellent ratio.

[Means for solving problems]

The above purpose focuses on the fact that the reproduction efficiency and inductance of a magnetic head are determined by the magnetic resistance of the magnetic core and the magnetic flux leakage between the magnetic cores, and the head impedance noise is determined by the resistance of the signal coil. A magnetic core consisting of a lower magnetic core formed in the upper and lower magnetic cores, an upper magnetic core formed through a gap spacer material, a signal coil, an insulating material, etc., and an operating gap formed by the gap spacer material of the upper and lower magnetic core connection parts; In a magnetic head consisting of a signal coil for signal detection, where a is the track width and b is the core width other than the working gap forming part, at least part of the core width satisfies 3≦b/a<3. This is achieved by setting the magnetic path length of the magnetic circuit formed by the upper and lower magnetic cores to 0.3 to 0.5 M.

[Effect]

When the front magnetic core width is a and the rear magnetic core width is b, the efficiency is low in the region where b / a is small and the output C is small, so the output C / J per inductance
In the region where 'T: is small and b/a is large, the efficiency approaches saturation, but since the inductance continues to increase uniformly, C/ and /T decrease. As a result, C/JT
The maximum value is taken at a certain value of b/a.

Assuming that the angle formed by the lower magnetic core and the upper ζn magnetic core at the rear end of the working gap is θ, increasing θ reduces magnetic flux leakage between the slopes of the re-magnetic core and increases efficiency, so C/J
T increases. Thereby there exists a minimum allowable value of θ.

If the distance between the upper and lower magnetic cores is l, in a region where 1/a is small, the leakage of magnetic flux between the upper and lower magnetic cores is large, the efficiency is low, and the output C is small, so C/JT: is small and l/ In a region where a is large, the efficiency decreases due to the increase in magnetic path length, the output C decreases, and C/, /T decreases.

Thereby, C/(π takes a maximum value at a certain value of l/a.

In addition, when the magnetic path length is reduced, the efficiency increases and C increases, but the coil 1t in the part that constitutes the magnetic path and its vicinity
fi decreases. This increases coil resistance and increases head impedance noise.

As a result, the C/N becomes maximum at a certain magnetic path length.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 shows a thin Il! according to the present invention! a is a cross-sectional view showing an embodiment of a magnetic head, and the structure of the magnetic head in this embodiment is such that a magnetic film 2 formed on a non-magnetic substrate l such as glass ceramic is used as a lower magnetic core; A magnetic circuit is formed by the magnetic film 2.3 using the magnetic film 3 as an upper magnetic core via the gap material 4 formed in the magnetic film 2, the signal coil 6, and the insulating material 5.

The magnetic films 2 and 3 are made of sendust, permalloy, amorphous alloy, etc. In this embodiment, C6-N based on C0 is used.
, -Z, were formed by RF sputtering using alloy films.

The gap material 4 can be made of a non-magnetic insulating material such as 5IOx, Algos, etc. or a non-magnetic conductor such as C, Z, etc. In this embodiment, C, is formed by sputtering.
A thickness of 3 μm was formed. The signal coil 6 is C.

The periphery is surrounded by an insulating material such as S r O.

FIG. 2 is a plan view of the upper magnetic core of the magnetic head shown in FIG. 1.

In FIGS. 1 and 2, head shape parameters are set as follows.

The spacing between the upper and lower magnetic cores! 1 The angle formed by the lower magnetic core 2 and the upper magnetic core 3 at the rear end of the working gap is θ, the front magnetic core width is a, the rear magnetic core width is s, and the magnetic path length is ff1.
Let it be m.

However, the front magnetic core width a is equal to the track width.

In this example,! −20μm, θ−60°.

A=20 um, b-100 μm. There is a relationship between these shape parameters and head performance as shown below. However, the head performance is 5μH.

Output C/J'T per unit inductance when output C and inductance L are: and 4 μH.

The evaluation was made using the ratio C/N of C to the noise size N.

Figure 3 shows the ratio b of the front magnetic core width to the rear magnetic core width.
It is a graph diagram showing the relationship between /a and the outputs c/ and /T, and the maximum value is reached when b/a is around 5.

If C/JT: is allowed to be -0.5 dB with respect to this maximum value, b/a becomes 3≦b/a≦8.

FIG. 4 is a graph showing changes in the output C/, /''T: with respect to the angle θ formed by the lower magnetic core and the upper magnetic core at the rear end of the gap, and the maximum value is at θ-π/2, -0,5
If dB is the allowable value, θ is shown as θ>π/4.

Fig. 5 is a graph showing the relationship between the ratio 1/a of the magnetic core width and the upper and lower magnetic core spacing and the output C, /J''U, where the maximum value is taken at a 2 g, -0,5d
If B is an allowable value, 1/a becomes 0, 541/a S 2.5.

FIG. 6 is a graph showing the relationship between the electric path length ff1m and the output versus noise, using a metal tape as the recording medium and track li T w 10 μm fog.

L-1μH, i of the magnetic core! i magnetic constant μ 400~2
I changed it to 000. As a result, the number of turns in the coil is 26.
As shown in the figure, the results vary from 1m to 20 turns and the coil spacing is 4μ.
The C/N reaches its maximum near 5 am. In addition, the coil thickness was varied from 2μ to 7μ, and the specific resistance ρ of the coil was
-1,7x 10-sΩ・m to 2.0XIO-@Ω・
Although the absolute value of C/N changed, there was no change in the fact that fmZo gave the maximum value around 45w.

FIG. 7 is a graph showing the results of an experiment similar to the above using an oxide tape as a recording medium. The conditions at this time were Tw-20 μm and L-0.5 μm, so the number of turns of the coil varied from 13 to 18 turns.

In this case as well, the coil thickness and specific resistance were changed in the same manner as above.

The results show that in the region of 400 μm with low magnetic permeability, 1 m-
It was found that for IJ-1000 to 2000, which have a high magnetic permeability of 0.35, the C/N becomes maximum near i m = 0.4.

As described above, in a thin film magnetic head for recording and reproducing video signals, etc., it is necessary to change various head shape parameters and physical specifications, for example, track width Tw: 10 to 60μ.
m, recording medium holding power +1c: 600-15000. , head inductance: 0.2-1.5 pH, in
Q: 117i3 [Ratio μ: 400-2000] Analytical calculations and experiments were performed, but regarding the C/N of the thin-film magnetic head, the optimum value for the magnetic path length of 1 m in the cough head (n-circuit) is 0.3
≦l m <0.5 fin range, preferably Q, 35
It was found that good values were given in the range of ≦1 m≦0.45 mm.

In addition, as shown in FIG. 8, the shape of the magnetic core 3 is as follows.
Similar results to those described above were also obtained when the portion from the front magnetic core to the rear magnetic core was formed to expand asymptotically.

Further, in the above embodiment, a two-layer signal coil is used, but the present invention is not limited to this.

〔Effect of the invention〕

As explained above, according to the present invention, by considering the magnetic resistance of the if score, the magnetic flux leakage, and the resistance of the coil, a magnetic core shape can be created that minimizes inductance, increases efficiency, and minimizes noise. obtained, increasing the output per unit inductance,
By improving the power-to-noise ratio, a thin film magnetic head with superior performance can be provided that eliminates the drawbacks of the prior art.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an embodiment of the thin-film magnetic head according to the present invention, FIG. 2 is a plan view of the upper magnetic core of the magnetic head shown in FIG. 1, and FIG. 3 shows the width of the front magnetic core and the rear magnetic field. A graph showing the relationship between the core width ratio and the output, Fig. 4 is a graph showing the change in output with respect to the angle formed by the lower magnetic core and the upper magnetic core at the end of the gap 9i, and Fig. 5 shows the relationship between the front magnetic core width and A graph showing the relationship between the ratio of the spacing between upper and lower magnetic cores and output, Figure 6 is a graph showing the relationship between magnetic path length and output vs. noise, and Figure 7 is a graph showing the relationship between magnetic path length and output versus noise. A graphical diagram showing the relationship between path length and output versus noise,
FIG. 8 is a plan view showing the other side of the upper magnetic core of the thin film magnetic head according to the present invention. DESCRIPTION OF SYMBOLS 1... Non-magnetic substrate, 2... Magnetic film for lower magnetic core, 3... Magnetic film for upper magnetic core, 4... Gap material, 5... Insulating material, 6... ( No. 3 coil. Give up ItH'! 1! 45 Fig. 1 1: Non-polar part 2: Lower part fade/ki, 7 i for core, biomembrane 3: Upper part 1) 7 use stone m, 17I order 4: Gear 9 F0 Neo 5° Neo 6° I Coil No. 1 Coil Fig. 2 Fig. 3% Fig. 4 7T/6yy3 ~ 0 (rod) Fig. 5 1/a Fig. 6 0.4 0.6 0.8! m (mm)

Claims (1)

[Claims] 1. A magnetic core consisting of a lower magnetic core formed on a non-magnetic substrate, an upper magnetic core formed via a gap spacer material, a signal coil, an insulating material, etc., and an upper and lower magnetic core connection part. In a magnetic head consisting of an operating gap formed by a gap spacer material and a signal coil for signal detection, the magnetic path length of the magnetic circuit formed by the upper and lower magnetic cores is expressed as m (mm). A thin film magnetic head characterized in that when 0.3≦lm≦0.5.